1. Field of Invention
The present invention relates to a power generator, and more particular to a portable driven generator which is capable of providing uniform and substantially constant electricity to an electrical appliance mounted on a bicycle frame.
2. Description of Related Arts
A conventional bicycle comprises a bicycle frame, a plurality of wheels rotatably mounted on the bicycle frame, a power generator mounted on the bicycle frame and communicated with the wheels, and an electrical appliance also mounted on the bicycle frame and is electrically connected to the power generator. When a user is riding on the bicycle, the wheels are driven to rotate, and the rotational movements of the wheels drive the power generator to generate a predetermined amount of electricity, which is then transmitted to the electrical appliance for operation thereof. Very often, the electrical appliance mentioned above is a LED light mounted at a rear portion of the bicycle frame so that when the user is riding the bicycle, electricity is generated to make the LED light illuminating.
There are several disadvantages related to the above-mentioned conventional bicycle. First, the electrical appliance, and the LED light in particular, acquires electricity from the power generator on a real-time basis. This implies that when the rider of the bicycle rides at varying speed, the rotational speed of the wheels cannot be kept substantially constant. Since the illumination generated by the electrical appliance depends on the power supplied, when less power is supplied, the intensity of the light is decreased. In other words, in a situation where the speed of the bicycle is not constant and fluctuates considerably, the intensity of the light generated by the electrical appliance fluctuates accordingly. This creates potential danger to the rider because when he or she is riding the bicycle at low speed, the intensity of the LED light may not be strong enough to alert other drivers on the road.
Second, for the conventional bicycle discussed above, the electrical appliance is built-in in the bicycle frame. The reason is that the power generator is specifically designed to supply electricity to that electrical appliance. The result is that the bicycle is not capable of accommodating other electrical appliances and the rider will not be able to connect his or her own electrical appliances to the bicycle.
Third, the power generator of the conventional bicycle is arranged to generate electricity when the wheels of the bicycle are rotating. The power generator usually comprises a driven shaft extended to contact with the wheels. Conventionally, there exist a lot of friction between the driven shaft and the wheels so that either the wheels or the driven shaft will be damaged very easily.